Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753605Ab0DQSuA (ORCPT ); Sat, 17 Apr 2010 14:50:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51331 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753285Ab0DQSt5 (ORCPT ); Sat, 17 Apr 2010 14:49:57 -0400 Message-ID: <4BCA02D1.2020608@redhat.com> Date: Sat, 17 Apr 2010 21:49:53 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: Glauber Costa CC: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jeremy Fitzhardinge , Marcelo Tosatti , Zachary Amsden Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock References: <1271356648-5108-1-git-send-email-glommer@redhat.com> <1271356648-5108-2-git-send-email-glommer@redhat.com> <4BCA026D.3070309@redhat.com> In-Reply-To: <4BCA026D.3070309@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 783 Lines: 31 On 04/17/2010 09:48 PM, Avi Kivity wrote: > >> >> +static u64 last_value = 0; > > Needs to be atomic64_t. > >> + >> cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) >> { >> struct pvclock_shadow_time shadow; >> unsigned version; >> cycle_t ret, offset; >> + u64 last; >> >> >> + do { >> + last = last_value; > > Otherwise, this assignment can see a partial update. On a 32-bit guest, that is. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/